Not necessarily. If a window is stretched to be slightly off the aspect ratio you'll see black bars and they'll look ugly, even if they're just a few pixels wide. If you stretch the icons to match this aspect ratio it won't look much different since the window's aspect ratio is only slightly off.

I tend to not mind the black bars, but it looks especially odd when you have black space around the edge of the map that players can see. When you can see some of the black that's part of the map it looks like the black bar is part of the map too. When you move in a way that fills the map control with actual icons (as opposed to black parts of the map), the black bar will suddenly look out of place.